Why would you want a 123d if you have a 135i and it probably costs less too!

because it's just cool. besides, it's nearly as fast as the 128i which isn't slow and it gets over 45 mpg hwy and like any turbodiesel plug in a little box and boom 30-35 hp and same in torque gains with not too much hindrance to the mileage

besides that, is there any other car out there that can beat a prius in hwy mileage and perform like the 123d?!

because it's just cool. besides, it's nearly as fast as the 128i which isn't slow and it gets over 45 mpg hwy and like any turbodiesel plug in a little box and boom 30-35 hp and same in torque gains with not too much hindrance to the mileage

besides that, is there any other car out there that can beat a prius in hwy mileage and perform like the 123d?!

That's exactly right. The 123d is like having your cake and eating it, too.